Cable



Nov. 26, 1940. F. UNTERBUSCH CABLE Filed Des. 12, 1936 Patented Nov. 26,1940 UNITED STAT-ES Franz Unterbusch, Colorne-Mplheim, Germany, assignorto Felton & Guillaume Carluverk Action-Gesellschaft, Coloxne-Mulhelm;Germnny Applicaflon Dooember 12. man, Serial o. 115,611

In Gummis 35 Deoemberl8,

2 Olaims. (c1.17429) The present invention' relates tb cables, und. morespeciflcally pertains to hlgh trequency cab1es of the a.ir spaceinsulatlon type.

It ha.s been expla.tned in Patent N0. 2.189,090

5 of February 6, 1940, that in cables with a. plurality f helicaleements, for instance, in the case of high Irequency cables with aconcentric return conductor und armourlng bring over lt; in the usualstranding, there is a danger 015 10 the he1ical metal bands serving asthe return conductor bucklin during the 1ayin8, and tha.t this bucklingcan be avoided lt the metal bands 01 the return conductor und the w1reamouring lying ovei it a.re applied with the saxne dil rection o! lay.Such buckling-in takes place when the cable is subjected to torsiona.lstresses. II a. cab1e, the elements 01 wh1ch arestranded in difierentlayers in opposlte directions, Ls twisted in such a way that theelements lying on the outside, Ior instance the hellcally providedarmouring wires, turn towards one another, then the bands ly1ng underthem will tum from one another und buckle-in a.s they cannot otherwiseescape.

-;: II helically stranded elements a.re twistecl, an increase ordecrease in the diameter ocurs when the position of the elements rematnsthe same,

and when the diametex remalns the sa.me there is an increase or decreasein the length, according as to whether the belical structure Winds in orout. The extent o! the changes 1s dependent on the diameter and on thepitch 01 the corresponding 1ayer.

The tollowing calculation shows that with cettain assumptions, and witha. suitable choice of the lengths of 1a.y the lengthenings orshortenings of the individual stranding elements, which arise in thecase 01 torsions beoome the same as regards direction and value.

If D1 is the diameter and S1 the length 01' lay cf the elements and L1the length 02 the elements in the return conductor 3 wh1le V 1s the testcab1e 1ength under consideratlon then V 45 Nl==a is the number of layinglength for the testab1e 1ength.

If D2 1s the diameter and S2 the length o1 lay of the elements and L2the length of the elements in the armouring 5 then is the number cflaying length for the test ca.- ble length.

With L1 und L2 ii1dicia.ting um: total length o! the elements in theretum conductor and the elements in the armmu'lng,

s1nce the length o1 the elements in the retum conductor a.nd thea.rmouring an one laying length 1s elements. Then there will be obtaineda. ri8ht angle tria.ngle with a baseline D1) r and with a height; of S1.The 1ength of the longest .s1de of this tria ngle 1s then /S1'+D1r' Inunwindlng not only a. layln'g length but an entire element there willresult a rinnt angle triangle with a. base 11ne N1D11r with a helghtN1S1 und the longest side 1s L1. It. follows therefrom:

L1=JD1NP+SPNP=SINH 1+%% If S1N1=V 1s introduced If the conductors arenow p1a.ced under torslon und the leng1sh 01 the conductor 1s V before Ythe application 01 a torsional force 'and V+AV1 alter the torsion andthe length o! the armour ls V before the torslon und V+AV2 at ter thetorsion it is.a.pparent that with each twist the number o1 1ay lengthswhich apply to the test length is increased' by one. After the tors1onthe number o! lay lengths is no langer N1 or N2 but N1+A und N2+A.

After a torslon 11 V+AV1 or V+AV2 a.re substituted 1or V.in Equation (4)and N1 +"A is substituted for N1 and N2+A 1s replacedby N2 the followingresults:

V "s2 7\T2'*'2T2 )7 II the two length changes AV1 und AV2 are equa.l noinner tensionswfll ar1so between the cnductors and the armouring und AV1will equal AV2 i! Dm 2A A 'I'he lengthenlnzs are thus the same in1:01:11

strandinglayersitthelengthsotla'yueintho very great laying lengths o1!the armouring, wh1ch 1s not desirable Ior stranding reasons. It 1stherefore proposed to choose a slightly sma.ller ratio between 1.5 and 2power. S1nce 1t has been assumed in the case o! the armouring that thediameters remain constant und must remaln coustant und this need not beexactly fulfllled, the proposed choice 01 the ratio between 1.5 und 2power 1s admlssible. The -(:h01ce 01 this ratio leads to admlssiblelaying lengths o1 the unter conductor and armouring.

S1nce cables accordlng to the inventlon, when drawn out, tend moreeasily to twlst than cables, the elements 01 which are stranded togetherin alternate directions, lt 1s advisable to prov1de over the. armourlngone or more layers 02 wires or bands, the direction o! which 1s oppositeto that of the armouring.

The accompanying drawing illustrates, by way of example, one Io1 m o1carryln out the Invention. 'I'he inner conductor l is separated from theouter'con'centric c0nductor 3 01 copper bands by an insulating hellx 201 polystyrol. Over the return conductor I there ls provided the leadsheathingl and the wire armouring 5.

The w1re armourlng and the bands of the return conductor 3 ha.ve thesame directlon ot-lay und their laying lengths S1 und S2 haveapproximately the same ratio as the squares 01 thelr diameters D1 und D2so that the following ratio holds good:

I cla.lm:

1. An -electrlcal ca.ble whereln the stresses tendingto buckle theelements 01 the cable are completely aVolded comprls ing, a. centralmetal conductor, a second conductor arranged over und substantiallyconcentric with respect tov the flrst conductor. yieldable insulatingmeans conslstlng of a continuous flexible spacer element interposedbetween sa.1d conductors providing air sbace insulation between theconductors whlch space may be altered durlng bending o! the ca.ble saldsecond conductor conslsting 01 a plurallty of metal bands helicallyarranged. adjacent oach other, an outer armouring consisting o1 aplurality o! helically arranged wires, said meta.l bands a.nd the Wiresextending along the length o! the centra.l conductor w1th the sa.medlrectlon o! lay and the mtlo of the la.y longthot the metal bands undthe wires falling withln a ratio tanze between the 1.5 power und thesquare 01 the d1-' ameters o! the second conduotor und the armourins.

2. An electrlcal ca.ble whereln the stresses tend- 1ng 1:0 buche theelement's of the cable a.re completely avoided oomprlsing, a ceutralmetal couductor, a. second oonductor arrangbd over und substanconductor. yleldable insula.tlng mea ns conslstlng o! a contlnuousflexible apacer (element interpooed between sa.ld conductors providinsa.ir spaoe msulation between the conductors wh1ch spaoe ma.y be altereddu.rlns bending o1 the cable. sald second oonductbr consistlng o! a.plun.llty o! metal bands hellcally arranged adjo.oent euch other, an outer arm ourlng consi.stlnz 01 a plura.llty o! helically arranged wlresthe dlrection otla.yofthemetalbandsandthewlrebelnzthesameandhnvlngtheloylengththereolof approxlmately-the sa.me ratio uthe aquares 01 the respective Magneten thuof.

I'RANZUN'IIRBUBCB.

conoentric w1th respect to the flrst

